Originally Posted By: benjammin
On a magnifier, the prismatic angle is facing towards the center of the lens, on a diffuser, it is facing away from the center, IIRC.

Yeah, you guys got me. I didn't consider the different types when I mentioned fresnel lens. The ones in bookmarks would be of the magnifying variety and wouldn't work. Whereas the ones you see stuck on the back of RV rear windows would be the diffuser variety, and MIGHT work. But buying a large RV model just so you could cut a 3/4" diameter circle out of the center of it might not the most cost-effective thing you could do!